A master cylinder of the generic type known from DE-OS 42 12 107 comprises a piston composed substantially of a piston head and a piston skirt bushing. To form a structural unit, a centrally arranged, integrally formed piston neck of the piston is positively fixed in the piston skirt bushing. To obtain a positive locking of the piston skirt bushing on the piston neck, a radially inwards directed rim on the end of the piston skirt bushing engages a peripheral groove of the piston neck. The end of the piston neck facing the piston rod comprises a spherical depression on which the piston rod ball is supported. The piston rod ball is retained in the piston skirt bushing by two spherical semi-shells which partially enclose the piston rod ball and comprise projections whose ends form radially inwards directed sections which engage a groove of the piston neck and thus assure a positive locking. Further, the piston skirt bushing is longitudinally displaceable in a guide sleeve of the master cylinder. This prior art configuration of a master cylinder requires a special sealing of the piston neck in the piston skirt bushing and a very high technical production quality of the spherical semi-shells which together with the spherical depression on the end of the piston neck assure a positive retention of the piston rod ball. In addition, the assembly of the prior art master cylinder is very complicated and therefore results in high manufacturing costs.